Film gate for projection apparatus



2 SHEETS-SHEET l R. M. GILE INVENTOK RKLHARD M. GILE.

ATTORNEYS FILM GATE FOR PROJECTION APPARATUS Oct. 21, 1952 Filed sept. 7, 1951 Oct. 2l, 1952 R M, GILE FOR PROJECTION APPARATUS FILM GATE ATTORNEYS 2 SHEETS-SHEET 2 P\\CHARO M. G\LE.

Filed Sept. 7, 1951 Patented Oct. 21, 1 952 FILM GATE FOR PROJECTION APPARATUS Richard M. Gile, Buffalo, N. Y., assigner to American Optical Company, Southbridge, Mass., a voluntary association of Massachusetts Application September i7, 1951, Serial No. 245,620

5 Claims. 1

This invention relates to microfilm projection apparatus and the like; and more particularly to a lm gate construction for use in such apparatus, which comprises a plurality of separable parts which may be made and assembled economically and which, when assembled, will provide exact positioning of strip film therein with respect to the curved object field of a projection objective of said apparatus as Well as a guideway having exceedingly close tolerances for the strip film therein or being passed at various speeds therethrough.

Microfilm has become a common medium for recording in compact form printed matter, documentary evidence, etc., and since such film is not required to be transported across a projection aperture in a step-by-step manner in exact successive equal amounts, as is conventional motion picture film, unperforated film may be employed to advantage and use made of a greater amount of the film in the transverse dimension thereof for the individual frames or picture carrying areas thereon. The result is that in a 16 mm. microfilm, for example, as much as mm. of the total width of the film is at times occupied by the picture bearing areas, with the result that sometimes no more than a half millimeter of clear film remains at either marginal edge of the film.

In microfilm readers provided with transparent pressure plates at the projection aperture for maintaining the individual frames or image bearing areas of the strip film in the focal plane of the objective, such narrow unused marginal portions are of minor concern. However, in a microfilm projector using such pressure plates considerable difficulty is experienced from the fact that the plates require expensive and cumbersome mechanical means for opening or separating the plates before the film starts to move and also for subsequent closing the plates after the film has assumed a completely stationary condition. Otherwise, the film might be irrepairably damaged. Also such pressure plates are liable to collect dust particles and other foreign matter, and have to be cleaned from time to time. Furthermore, at times foreign matter may become embedded in the plastic material of the microfilm and this may scratch the surfaces of the pressure plates as the film moves therebetween. Such scratches, it will be readily appreciated 'arevery objectionable since they will lie substantially in the same plane as the picture upon the film and consequently will fog ro diffuse the projected image.

For these and other reasons it has been found desirable to provide in microfilm projection apparatus, in place of pressure plates, a curved lm gate which will prevent buckling of the film during projection and which accurately' curves the film to a predetermined curvature which will most nearly t the curvature of field of the objective of the apparatus. Such a microfilm projector employing a curve film gate is shown in prior Patent No. 2,482,666 which issued' September 20, 1949.

While such a curved film gate at first glance might appear to be a comparatively simple device, it nevertheless has been found in practice to be a difficult thing to manufacture accurately to the several exacting tolerances required and still have some function as intended over long periods of time. For example, such a curved film gate must support the film accurately in a predetermined curvature according to the objective employed, must support the film at opposite edges in order to maintain such film curvature, such support means for the edges must be' wear resistant and as smooth as possible, must be narrow in order to provide a maximum clear aperture therebetween, and must have confining walls outwardly thereof which have a very accurate width therebetween for guiding the film. Furthermore, the gate must not scratch the picture carrying area of the film. Also the gate must have a cover member but such cover member must normally closely confine the clear side edges of the film at the projection aperture while allowing free movement thereof. It must not contact the picture areas of the film and it should be free for movement away from the gate member for insertiony of an intermediate portion of strip film while suspended between a pair of supporting reels. On the other hand, the cover member must not allow the film to move out of the guideway provided therefor while the lm is traversing the projection aperture at high and variable speeds. Furthermore, at times a double thickness of film, such as a film splice, must be accommodated by the gate. Parts of the gate and cover members contacting the film must not only be accurately spaced to properly accommodate the film and splices therein,rr accurately curved to fit the predeterminedl requirements of the associated objective or objectives, but also should be, for best results and minimum friction, as smooth as possible and as hard as possible to withstand the repeated abrasive wear of the strip nlm sliding thereover, and of course it is desirable to have a gate possessing all ofthese advantages also be inexpensive to .make and install. It has been found that a gate possessing these desirable features may be had by making same of several parts and assembling these parts in accordance with the teachings of the present invention.

It is, accordingly, an object of the present invention to provide for strip nlm projectors, or the like, a film gate construction comprising a pair of accurately spaced film guiding rails of small carefully controlled transverse dimension or thickness and curved to the exact predetermined curvature required for positioning film in the curved object field of a projection objective. It is also an object of the invention to make certain of the parts of such a film gate construction as separate elements so that they may be individually formed to exact predetermined dimensions and separately treated or processed as required before assembly, and also so that certain of said parts may be` readily adjustable rel-v ative to other parts thereof for accurate positioningduring the assembly of. the gate.

It: is an additional objectV ofthe invention to providea lm. gate constructionhaving a. pair of fllrn'guiding'rails .which may be individually fab ricated of material best suited for. the purpose and individuallytreated, or a plurality thereof fabricated and' processed;v as desired, as a group before being assembled inrindividual lm'gateA constructions.

It is a further object of the invention to providein such a curvedlm gate having a normally stationary gate assembly and cover means therefor, a construction and' arrangement of parts which allows fllmguiding surfaces thereof to' be readily adjusted. into exact. predetermined spacingrelativetolm confining portions of the cover guide means. or readjusted readily'to a different exact' film'. thickness or; spacing when required.

Other Objects and advantages of the. invention will. become apparent from thedetailed de.-

scriptionxwhich follows. when. taken in conjunction with. theV accompanying drawing in which:

Fig. 1 is a front elevational view ofa microfilm gate construction embodying the presentv invention. and showingiilm extending therethrough;

Fig. 2 is a side. elevational view of the structure of Fig. 1 and showing a handle for bodily shifting the gate;

Fig. 3 is a plan. Viewv of' the structure of Fig; 1;

Fig, 4. is ar plan view; partly in section, of the y gate assembly offFig. 1;

Fig. 5 is a perspective exploded view of the cover assembly of Fig; 1;

Fig. 6 isl a perspective exploded view ofthe gate assembly in Fig: 1;

Fig.. 7 is a sectional. viewtaken substantially on section lines 1-1 of Fig. 3;

Fig. 8 is a perspective view' of guide rails which may be used in the structure of Fig. l.; and

Fig. 9 isr a modification of a part of the structure of Fig. 1.

Referring to the drawing in detail, there is shown in Figs. l, 2, 3v and 4 a iilm gate construction Illl comprising a gate assembly I I and a cover assembly I2. A strip ofV film extending through the gate isshown at I3. The gate assembly comprises a pair of spacing blocks I4 and I5 spaced from each other an amount sufficient to accommodate a rectangular projection apertureA I6 therebetween. In fact it may be convenient to have the blocks actually define edges of the aperture, as in the present instance. The blocksv I4 and I5 may be individually finished or a plurality groupedtogether and finished at one time upon opposite edges thereof so as to form upon each block a pair of abutment surfaces I8 and I9 which are an exact predetermined distance from each other. When a pair of these blocks properly drilled to receive securing screws or bolts are employed as spacer members a pair of guide rail members 20 and 22 may be clamped thereto. The guide rail members are of accurately controlled thickness and are provided along their upper edges with a pair of accurately curved upper surfaces 24 and 26, respectively, which serve as supporting means for marginal edge portions of strip filmv extendingA through the gate assembly. In order to maintain these guide rails in position in the assembly and to prevent lateral displacement of the fllma pair of side bars 28 and 3U are provided' and are clamped against the outer sides of the rails preferably by means of sets of screws or the like 32 extending therethrough and through the guide rails and threaded into opposite sides of each spacing block. Thus, facing sidewall portions thereof may bexmadetoaccuratelyreceive and laterally confine the film strip. Itis preferableto provide such a set of four screws for each side bar and adjacent guide rail soV that same may be individually securediin place. For reasonswhich will be later explained the openings' provided. in*` the guide rails 20 andr 22 are madeslightly oversized with respect to the size of the bolts or screws 32 employed for clamping the parts together and, accordingly, the position` of each guide rail may be adjusted in a vertical. or longitudinal direction slight amounts when required. Guide railst20 and 22 in the present construction are recessed slightly as indicated atZII' and 22' so as not to block offedge portions'of` the picture forming light rays.

By providing. a gate assembly composed of a plurality of parts',A as just described', it ispossible tol exactly finish the opposite abutment surface I8 and I9 on they spacing blocks Il and I5 accurately relative to each other, individually or in groups', and to employ therewith guide rails which may. be formed of relatively hard sheetmaterials, such as tool steel or the like, andto heat treat same to provide any preferred microgranular condition. Also, it will be easy to grind andpolish the film supporting edges thereof, individually or in groups, to an exact predetermined curvature or curvatures as required. Furthermore, it is possible to employ as the plate-like material from which these guide rail members arefo'rmed, either sheet metal of exactly the desired thickness or to individually accurately finish these plate-like members to such a thickness with little difficulty and by common machining methods.

The component parts ofthe gate assembly II are shown by an exploded view in Fig. 6 and it will be seen that the side bar 28 is provided with an upper extension 28 in which aligned threaded openings 33 are arranged adjacent opposite ends thereof for receiving a pair of pintles 3l upon which the cover assembly I2 may be hinged. As shown in Fig. 7 the cover assembly is arranged for movement from an operative position overlying film supported by the film gate assembly to a raised' or inoperative position for allowing such nlm to be inserted or removed as desired froma passageway or: guideway 3GV formed therebetween.

The cover may be made asl one single machined part but preferably is a built-up assembly whichi comprises, in the preferred construction as shown by Figs.l l, 2v and 3 and in details in Fig. 5, a side bar 4W having downwardly' extending projections 40' adjacent opposite ends` thereof. These projections are provided with aligned openingsfor receiving the pintles 34 and are so shapedas to allow a hinging action' of the bar 40 relative to the gate assembly` H and the lower side bar 28 thereof. A pair of confining guide rails 42 and 44 are provided to overlie the guide rails2 and 22 andare held in spaced relation by an upper pair of spacing blocks 44 and 46. These blocks are of such size and so spaced from each other as to form between the guide' rails and the spacing blocks a rectangular l opening aligned with the projection aperture I6 l when a'pair of securing screws or bolts 48` are extended through these members and into a threaded side bar 50 which is preferably of relatively heavy material. The side bar 50 serves as means to normally'hold the cover assembly in closed position overlying the gate assembly Y andthe guideway 36.

Thus, slight movement of the cover assembly is allowed when required during travel of a thick portion of lm strip through the gate.

'Normally the several parts constituting the cover assembly will be accurately nished and then assembled and secured in place by the screws or bolts 48 after which the guide rails of the lower gate assembly may be adjusted vertically toward the confining guide rails 42-44 andinto an exact predetermined spaced relation relative thereto, preferably formed by a strip of film, or the like, of exact thickness desired positioned therebetween after which the clamping bolts 32 and 33 may be tightened clamping the parts to spacing blocks I4 and I5.

In the lilm gate construction shown, the bottom surfaces of the spacing blocksk I4 and I5 are grooved in the general direction of travel of the nlm as indicated at 52, the purpose for such grooves being to accommodate upwardly pressed ball detents (not shown)r or the like, for maintaining the entire gate construction including the gate assembly and cover assembly in a central position relative to the optical axis of a projector as well as for allowing a lateral shifting of the gateequal amounts of either side of such central position when desired. For example, when'such a lm gate is being employed with an objective of relatively high magnification it may be desirable to shift the gate as well as the lm in order that all portionsr of an individual frame may be aligned therewith for projection purposes. In order to allow such lateral shifting of the nlm gate and still have the gate assembly stay in place relative to the projection apparatus, there are provided in the side bars of the gate assembly cylindrical lrods 54 and 555 which are intended to extend into or through aligned openings in the projector housing. This will knormally prevent upward movement of the assembly but allow sidewise shifting of the film and gate. The forward rod 54 is provided with a handle 58 for facilitating such shifting of the film gate.

If reference is made to Fig. 7 it will be seen that the pint-lc or pivot means 34 for the cover assembly is located above a horizontal plane passing through the guideway 3B at the center of the gate. This is so that the cover assembly may be swung upwardly readily without having overlapping lip or edge portions of the cover assembly bind and interfere with part of the gate assembly during such pivotal action. To further assure that the gate and cover assemblies are normally maintained in proper operative relationship during movement of strip lm therethrough, notwithstanding the fact that at times and 'cause same to fly upwardly, a pin 601s provided centrally in the forward bar 50 of the cover assembly and has its lower end portion ,arranged to extend downwardly into a tapered recess 62 provided thereforv in the forward side bar of the gate assembly I2. f

Fig. 8 shows a group of rail members, like 20 and 22, which may be individually blanked, nished to proper thickness, heat treated and then clamped together for a nal grinding and polishingof the upper surfaces 63 thereon to the exact compound curvature desired, not only to accommodate near the centers thereof the lm contacting curve E3 required but also the rounded end portions 63". Pairs of oversized holes are shown in each end of each side rail and preferably these will be forme-d before hardening of the rails. In somewhat similar manner a group of blocks IIIy and I5 may be clamped together and simultaneously ground. to form surfaces I8 and thereafter reversed to form surfaces I9 of exact spacing relation thereto.

In Fig. 9 a slightly different modification is shown. The spacing and supporting means for the lower gate assembly may comprise a main supporting member 54 having a central projection aperture 68 formed therein and being provided at opposite sides of this aperture with upstanding projections B8 and 69 having on opposite edge portions thereof accurately spaced abutment surfaces IIJ in parallel relation to each other. These projections are provided with threaded openings for receiving the clamping screws in a manner similar` to that employed in the blocks I4 and I5 of Fig. 1. While a little more room is required in the axial direction in a projector for accommodating'a film gate having such a main supporting member such might, nevertheiess, be desirable at times. It should be evident, however, that in such a construction after the guide rails and side bars have been loosely secured to opposite sides of these upstanding projections 68 and 69 these guide rails may be moved vertically toward the cover plate or assembly employed therewith and into exact predetermined spaced relation with respect to the confining guide rails 42 and 44 thereon by acess through the projection aperture 65 thereo While as much as 15 mm. may be possible in width of picture area on a 16 mm. lm accommodated by a iilm gate of the present construction, a preferred spacing between film guiding rails for this size film is `approximately 14 mm. with a thickness of each rail being approximately one millimeter or slightly more. Obviously, similar proportions may be employed for film gates following the teachings of the present invention but adapted for use with other dierent standard widths of nlm.

Having described my invention, I claim:

l. A projector film gate construction comprising a gate assembly and cover means carried thereby, said gate assembly comprising means for positioning said gate assembly in operative position upon a projector, or the like, and including a pair of spacing blocks disposed in spaced relation to each other so as to accommodate a projection aperture therebetween, said spacing blocks having accurately spaced abutment surfaces formed on opposite sides thereof, a pair of plate-like guide rails of accurately controlled thickness disposed in spaced substantially exergue wall portions .thereon :for conning'stripi lm of a predetermined size. whenilocated therebetween -tlagainst'any appreciablellateralrdisplacement, and

means for securing said side .bars .toisaid spaca; ing blocks and for clamping saidguide rails ,.itherebetweem saidY gm'de rails: having accurately.

`1 formed: fi'lmfeguiding surfaces 'of predetermined curvaturexthereon.

2. .Afprojectorzfilm'gate .assembly comprising f: means for. positioningisa'id'gate assemblytin oper- 'ativei positionupon. a: projector,4 or.the= like.said.i

@means including a pair ofv spacing .blocks disposed .rinLnormally .fixed spaced relation to. each other Iso .asitfto,.accommoriateia tprojection aperture -then'ebetween said spacing blocks having accufzrately spaced abutment surfaces'formed on oppositesides thereof apainof plate-like guide rails 'tof Aaccurately controlled V.thicknessV disposedin :spaced substantially parallel relation at opposite sides" of 'said spacing` 'blocks so .as` toY .accommodate `saidxproje'ction. aperture therebetween; a l pair of 'iside bars located'outwardly of said guide railsfor fconnngstriplm of a predetermined size when located therebetween against any appreciable lateral displacement; vandmeans for securing said side/bars toLsaidspacing blocks and for clamping -said guide. rails therebetween, 'said Yguiderails being detachable from: said spacing blocksl and :having: accurately Aformed film-guiding surfaces .of lpredetermined lcurvature formed thereon.

3.,.A proj ector 'lm' gate construction compris- .zing-,a gate assembly and -cover'carried thereby, said fgatexassembly4 comprising means for posiitioning rsaid gatei assemblyrin/operative` position Lupena projector; or the'like,and including a pair oft spacing blocks4 disposed :in spacedxrelation to i each' other so as to accommodate-.a projection aperture therebetweem said `spacing .blocks hav- :ing accurately spaced abutment surfaces formed --cn opposite sides thereof, a pair. of plate-like A'.'guide'railsof accurately controlled thickness disi V; posediin'spaced'substantially parallel relation rat opposite sides of vvsaid Vspacingblocks so as to :accommodate said projection aperture therebe- .tWeen,` a pair of side bars located voutwardly of -said guide'rails andihaving ysidewall portions thereon for confining strip film of a predeter- :fmined-size *when located .therebetween against K.any1 appreciable lateral displacement, meansifor securing said-sidebarsito said spacingblocksand for clamping said guide rails therebetweemssaid guiderails havingaccuratelyformed hlm-guiding I surfaces ofA predetermined curvature thereon; and .mea-nsipivotally. connecting-said cover' to. one of saidside-barSfso as-to allowupward movement of i-saidcover relative-to saidl gate assembly for insertion ofY strip film therebetween.

4. A projector film gate -constructioncomprising a gate assembly and a cover assembly carried .therebysaid gateassembly comprising means for :positioning said. gate assemblyin operative posi- ;;tion.11pon aprojector, or theillke; and includinga t pair Vof spacingsblocksdisposedin spaced relation ftof'eachV other so as to4 accommodate a projection .aperture therebetween, said spacing blockshaving-accurately.' spaced l abutment surfaces formed .onfopposite sides thereof, a pair of lower .platellike, guide rails of accurately .controlled thickness disposedin spaced substantially parallel relation atfoppositesideszof said spacing blocksso as to accommodate. vsaid projection aperture therebetween,. apair` of side barsflocated outwardly of isaidguide. railseand having sidewall portions Athereon iforconining 'strip filmt ofxa vpredetermined size Awhen located therebetween.' against any: appreciablelateral displacement, ymeans for `securing said: side barsto-said Spacing blocks and `forzclamping said' guide rails therebetween, said llowerguidefrails havingaccurately formed lm- `guiding surfaces -of predetermined 1 curvature thereon, said cover assembly comprising ,spacing blocks and apair of `upper hlm-'confining guide `rails secured thereto so as .to be inipredetermined spaced relation tov each' other; andmeans on vsaid cover assembly engaging -said gate assembly `so as to normally positibnsad confining yguide rails in position directly above and in predetermined spaced relatioirtoy saidflower-guide rails during use thereof.

5. A projectorfllm4 gateV construction comprising.a,gate assemblyand. coverv means carried thereby, said gate assembly comprising means for positioning saidgateassembly in operativepositionupon aprojectonor the like, and including a pair ofy spacing blocks ,disposed in spaced relation .to each-other so as to accommodate a projection aperture therebetween, said spacing blocks 'having accurately spaced abutment `surfaces formedon oppositesides thereof, a pair` of lower plate-like guide rails yof accurately controlled thickness disposed in spaced substantially parallel relation at opposite sides `of said. rspacing blocks solas to' accommodate said projection aperture therebetween, ap'air of side bars locatedlout- Wardly of saidguide rails and having side wail v portions -thereon for conilning` strip' film of .a predetermined size when located` therebetween -against any appreciable lateral displacement, means'for-securing said side bars to said spacing blocks and for clamping said guide rails' therebetween, ysaid 'lower guide rails having accurately formed film-guiding vsurfaces-of predetermined curvature thereon;y said cover means comprising spacing blocks and a pair of upper film-confining guide rails removablysecured thereto so as to be in predetermined spaced relation to each other, and means for hingedly securing said cover means to a side bar of said gate assembly with said confining guide rails disposed directly above Vand in predetermined spaced relation to said lower guide rails.

RICHARD'fM. GILE.

No references cited. 

